lib/addns/dnsquery_srv.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify
   3  *  it under the terms of the GNU General Public License as published by
   4  *  the Free Software Foundation; either version 3 of the License, or
   5  *  (at your option) any later version.
   6  *
   7  *  This program is distributed in the hope that it will be useful,
   8  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *  GNU General Public License for more details.
  11  *
  12  *  You should have received a copy of the GNU General Public License
  13  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  14  */
  15
  16 #include "replace.h"
  17 #include "dnsquery.h"
  18 #include "dnsquery_srv.h"
  19 #include "lib/util/debug.h"
  20 #include "lib/util/tevent_ntstatus.h"
  21 #include "lib/util/talloc_stack.h"
  22 #include "lib/util/samba_util.h"
  23 #include "librpc/gen_ndr/dns.h"
  24 #include "librpc/ndr/libndr.h"
  25
  26 /*
  27  * For an array of dns_rr_srv records, issue A/AAAA queries for those
  28  * records where the initial reply did not return IP addresses.
  29  */
  30
  31 struct dns_rr_srv_fill_state {
  32         struct dns_rr_srv *srvs;
  33         size_t num_srvs;
  34
  35         struct tevent_req **subreqs;
  36         size_t num_outstanding;
  37 };
  38
  39 static void dns_rr_srv_fill_done_a(struct tevent_req *subreq);
  40 #if defined(HAVE_IPV6)
  41 static void dns_rr_srv_fill_done_aaaa(struct tevent_req *subreq);
  42 #endif
  43 static void dns_rr_srv_fill_timedout(struct tevent_req *subreq);
  44
  45 static struct tevent_req *dns_rr_srv_fill_send(
  46         TALLOC_CTX *mem_ctx,
  47         struct tevent_context *ev,
  48         struct dns_rr_srv *srvs,
  49         size_t num_srvs,
  50         uint32_t timeout)
  51 {
  52         struct tevent_req *req = NULL, *subreq = NULL;
  53         struct dns_rr_srv_fill_state *state = NULL;
  54         size_t i, num_subreqs;
  55
  56         req = tevent_req_create(mem_ctx, &state, struct dns_rr_srv_fill_state);
  57         if (req == NULL) {
  58                 return NULL;
  59         }
  60         state->srvs = srvs;
  61         state->num_srvs = num_srvs;
  62
  63         /*
  64          * Without IPv6 we only use half of this, but who does not
  65          * have IPv6 these days?
  66          */
  67         num_subreqs = num_srvs * 2;
  68
  69         state->subreqs = talloc_zero_array(
  70                 state, struct tevent_req *, num_subreqs);
  71         if (tevent_req_nomem(state->subreqs, req)) {
  72                 return tevent_req_post(req, ev);
  73         }
  74
  75         for (i=0; i<num_srvs; i++) {
  76
  77                 if (srvs[i].hostname == NULL) {
  78                         continue;
  79                 }
  80                 if (srvs[i].ss_s != NULL) {
  81                         /* IP address returned in SRV record. */
  82                         continue;
  83                 }
  84
  85                 subreq = ads_dns_lookup_a_send(
  86                         state->subreqs, ev, srvs[i].hostname);
  87                 if (tevent_req_nomem(subreq, req)) {
  88                         TALLOC_FREE(state->subreqs);
  89                         return tevent_req_post(req, ev);
  90                 }
  91                 tevent_req_set_callback(
  92                         subreq, dns_rr_srv_fill_done_a, req);
  93
  94                 state->subreqs[i*2] = subreq;
  95                 state->num_outstanding += 1;
  96
  97 #if defined(HAVE_IPV6)
  98                 subreq = ads_dns_lookup_aaaa_send(
  99                         state->subreqs, ev, srvs[i].hostname);
 100                 if (tevent_req_nomem(subreq, req)) {
 101                         TALLOC_FREE(state->subreqs);
 102                         return tevent_req_post(req, ev);
 103                 }
 104                 tevent_req_set_callback(
 105                         subreq, dns_rr_srv_fill_done_aaaa, req);
 106
 107                 state->subreqs[i*2+1] = subreq;
 108                 state->num_outstanding += 1;
 109 #endif
 110         }
 111
 112         if (state->num_outstanding == 0) {
 113                 tevent_req_done(req);
 114                 return tevent_req_post(req, ev);
 115         }
 116
 117         subreq = tevent_wakeup_send(
 118                 state->subreqs,
 119                 ev,
 120                 tevent_timeval_current_ofs(timeout, 0));
 121         if (tevent_req_nomem(subreq, req)) {
 122                 return tevent_req_post(req, ev);
 123         }
 124         tevent_req_set_callback(subreq, dns_rr_srv_fill_timedout, req);
 125
 126         return req;
 127 }
 128
 129 static void dns_rr_srv_fill_done(
 130         struct tevent_req *subreq,
 131         NTSTATUS (*recv_fn)(
 132                 struct tevent_req *req,
 133                 TALLOC_CTX *mem_ctx,
 134                 uint8_t *rcode_out,
 135                 size_t *num_names_out,
 136                 char ***hostnames_out,
 137                 struct samba_sockaddr **addrs_out))
 138 {
 139         struct tevent_req *req = tevent_req_callback_data(
 140                 subreq, struct tevent_req);
 141         struct dns_rr_srv_fill_state *state = tevent_req_data(
 142                 req, struct dns_rr_srv_fill_state);
 143         size_t num_subreqs = talloc_array_length(state->subreqs);
 144         struct dns_rr_srv *srv = NULL;
 145         size_t num_ips;
 146         struct sockaddr_storage *tmp = NULL;
 147         uint8_t rcode = 0;
 148         char **hostnames_out = NULL;
 149         struct samba_sockaddr *addrs = NULL;
 150         size_t num_addrs = 0;
 151         NTSTATUS status;
 152         size_t i;
 153         const char *ip_dbg_str = (recv_fn == ads_dns_lookup_a_recv) ?
 154                                  "A" : "AAAA";
 155
 156         /*
 157          * This loop walks all potential subreqs. Typical setups won't
 158          * have more than a few DCs. If you have really many DCs
 159          * (hundreds) and a DNS that doesn't return the DC IPs in the
 160          * SRV reply, you have bigger problems than this loop linearly
 161          * walking a pointer array. This is theoretically O(n^2), but
 162          * probably the DNS roundtrip time outweights this by a
 163          * lot. And we have a global timeout on this whole
 164          * dns_rr_srv_fill routine.
 165          */
 166         for (i=0; i<num_subreqs; i++) {
 167                 if (state->subreqs[i] == subreq) {
 168                         state->subreqs[i] = NULL;
 169                         break;
 170                 }
 171         }
 172         if (i == num_subreqs) {
 173                 tevent_req_nterror(req, NT_STATUS_INTERNAL_ERROR);
 174                 return;
 175         }
 176
 177         srv = &state->srvs[i/2]; /* 2 subreq per srv */
 178
 179         status = recv_fn(
 180                 subreq,
 181                 state,
 182                 &rcode,
 183                 &num_addrs,
 184                 &hostnames_out,
 185                 &addrs);
 186         TALLOC_FREE(subreq);
 187
 188         if (!NT_STATUS_IS_OK(status)) {
 189                 DBG_INFO("async DNS %s lookup for %s returned %s\n",
 190                          ip_dbg_str,
 191                          srv->hostname,
 192                          nt_errstr(status));
 193                 num_addrs = 0;
 194                 goto done;
 195         }
 196
 197         if (rcode != DNS_RCODE_OK) {
 198                 DBG_INFO("async DNS %s lookup for %s returned DNS code "
 199                          "%"PRIu8"\n",
 200                          ip_dbg_str,
 201                          srv->hostname,
 202                          rcode);
 203                 num_addrs = 0;
 204                 goto done;
 205         }
 206
 207         if (num_addrs == 0) {
 208                 DBG_INFO("async DNS %s lookup for %s returned 0 addresses.\n",
 209                          ip_dbg_str,
 210                          srv->hostname);
 211                 goto done;
 212         }
 213
 214         num_ips = talloc_array_length(srv->ss_s);
 215
 216         if (num_ips + num_addrs < num_addrs) {
 217                 /* overflow */
 218                 goto done;
 219         }
 220
 221         tmp = talloc_realloc(
 222                 state->srvs,
 223                 srv->ss_s,
 224                 struct sockaddr_storage,
 225                 num_ips + num_addrs);
 226         if (tmp == NULL) {
 227                 goto done;
 228         }
 229
 230         for (i=0; i<num_addrs; i++) {
 231                 char addr[INET6_ADDRSTRLEN];
 232                 DBG_INFO("async DNS %s lookup for %s [%zu] got %s -> %s\n",
 233                          ip_dbg_str,
 234                          srv->hostname,
 235                          i,
 236                          hostnames_out[i],
 237                          print_sockaddr(addr, sizeof(addr), &addrs[i].u.ss));
 238                 tmp[num_ips + i] = addrs[i].u.ss;
 239         }
 240         srv->ss_s = tmp;
 241         srv->num_ips = num_ips + num_addrs;
 242
 243 done:
 244         state->num_outstanding -= 1;
 245         if (state->num_outstanding == 0) {
 246                 tevent_req_done(req);
 247         }
 248 }
 249
 250 static void dns_rr_srv_fill_done_a(struct tevent_req *subreq)
 251 {
 252         dns_rr_srv_fill_done(subreq, ads_dns_lookup_a_recv);
 253 }
 254
 255 #if defined(HAVE_IPV6)
 256 static void dns_rr_srv_fill_done_aaaa(struct tevent_req *subreq)
 257 {
 258         dns_rr_srv_fill_done(subreq, ads_dns_lookup_aaaa_recv);
 259 }
 260 #endif
 261
 262 static void dns_rr_srv_fill_timedout(struct tevent_req *subreq)
 263 {
 264         struct tevent_req *req = tevent_req_callback_data(
 265                 subreq, struct tevent_req);
 266         struct dns_rr_srv_fill_state *state = tevent_req_data(
 267                 req, struct dns_rr_srv_fill_state);
 268         bool ok;
 269
 270         if (DEBUGLEVEL >= DBGLVL_INFO) {
 271                 size_t i, num_addrs = 0;
 272
 273                 for (i=0; i<state->num_srvs; i++) {
 274                         /*
 275                          * Count for the debug. Code that fills this
 276                          * in ensures no wrap.
 277                          */
 278                         num_addrs += state->srvs[i].num_ips;
 279                 }
 280
 281                 DBG_INFO("async DNS lookup timed out after %zu addresses "
 282                          "returned (not an error)\n",
 283                          num_addrs);
 284         }
 285
 286         ok = tevent_wakeup_recv(subreq);
 287         TALLOC_FREE(subreq);
 288         TALLOC_FREE(state->subreqs);
 289         if (!ok) {
 290                 tevent_req_oom(subreq);
 291                 return;
 292         }
 293
 294         tevent_req_done(req);
 295 }
 296
 297 static NTSTATUS dns_rr_srv_fill_recv(struct tevent_req *req)
 298 {
 299         return tevent_req_simple_recv_ntstatus(req);
 300 }
 301
 302 /*
 303  * Request a SRV record and fill in the A/AAAA records if the SRV
 304  * record did not carry them.
 305  */
 306
 307 struct ads_dns_query_srv_state {
 308         struct tevent_context *ev;
 309         uint32_t async_dns_timeout;
 310         const char *query;
 311
 312         struct tevent_req *fill_req;
 313         struct tevent_req *timeout_req;
 314         struct dns_rr_srv *srvs;
 315         size_t num_srvs;
 316 };
 317
 318 static void ads_dns_query_srv_site_aware_done(struct tevent_req *subreq);
 319 static void ads_dns_query_srv_done(struct tevent_req *subreq);
 320 static void ads_dns_query_srv_filled(struct tevent_req *subreq);
 321
 322 struct tevent_req *ads_dns_query_srv_send(
 323         TALLOC_CTX *mem_ctx,
 324         struct tevent_context *ev,
 325         uint32_t async_dns_timeout,
 326         const char *sitename,
 327         const char *query)
 328 {
 329         struct tevent_req *req = NULL, *subreq = NULL;
 330         struct ads_dns_query_srv_state *state = NULL;
 331
 332         req = tevent_req_create(
 333                 mem_ctx, &state, struct ads_dns_query_srv_state);
 334         if (req == NULL) {
 335                 return NULL;
 336         }
 337         state->ev = ev;
 338         state->async_dns_timeout = async_dns_timeout;
 339         state->query = query;
 340
 341         if ((sitename != NULL) && (sitename[0] != '\0')) {
 342                 char *after_tcp = NULL;
 343                 char *site_aware = NULL;
 344
 345                 /*
 346                  * ".<SITENAME>._sites" comes after "._tcp."
 347                  */
 348                 after_tcp = strstr(state->query, "._tcp.");
 349                 if (after_tcp == NULL) {
 350                         tevent_req_nterror(req, NT_STATUS_INVALID_PARAMETER);
 351                         return tevent_req_post(req, ev);
 352                 }
 353                 after_tcp += 6; /* strlen("._tcp.") */
 354
 355                 site_aware = talloc_asprintf(
 356                         state,
 357                         "%.*s%s._sites.%s",
 358                         (int)(after_tcp - state->query),
 359                         state->query,
 360                         sitename,
 361                         after_tcp);
 362                 if (tevent_req_nomem(site_aware, req)) {
 363                         return tevent_req_post(req, ev);
 364                 }
 365
 366                 subreq = ads_dns_lookup_srv_send(state, ev, site_aware);
 367                 if (tevent_req_nomem(subreq, req)) {
 368                         return tevent_req_post(req, ev);
 369                 }
 370                 tevent_req_set_callback(
 371                         subreq, ads_dns_query_srv_site_aware_done, req);
 372                 return req;
 373         }
 374
 375         subreq = ads_dns_lookup_srv_send(state, state->ev, state->query);
 376         if (tevent_req_nomem(subreq, req)) {
 377                 return tevent_req_post(req, ev);
 378         }
 379         tevent_req_set_callback(subreq, ads_dns_query_srv_done, req);
 380         return req;
 381 }
 382
 383 static void ads_dns_query_srv_site_aware_done(struct tevent_req *subreq)
 384 {
 385         struct tevent_req *req = tevent_req_callback_data(
 386                 subreq, struct tevent_req);
 387         struct ads_dns_query_srv_state *state = tevent_req_data(
 388                 req, struct ads_dns_query_srv_state);
 389         NTSTATUS status;
 390
 391         status = ads_dns_lookup_srv_recv(
 392                 subreq, state, &state->srvs, &state->num_srvs);
 393         TALLOC_FREE(subreq);
 394
 395         if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
 396             NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
 397                 tevent_req_nterror(req, status);
 398                 return;
 399         }
 400
 401         if (NT_STATUS_IS_OK(status) && (state->num_srvs != 0)) {
 402                 if (state->async_dns_timeout == 0) {
 403                         tevent_req_done(req);
 404                         return;
 405                 }
 406
 407                 subreq = dns_rr_srv_fill_send(
 408                         state,
 409                         state->ev,
 410                         state->srvs,
 411                         state->num_srvs,
 412                         state->async_dns_timeout);
 413                 if (tevent_req_nomem(subreq, req)) {
 414                         return;
 415                 }
 416                 tevent_req_set_callback(
 417                         subreq, ads_dns_query_srv_filled, req);
 418                 return;
 419         }
 420
 421         subreq = ads_dns_lookup_srv_send(state, state->ev, state->query);
 422         if (tevent_req_nomem(subreq, req)) {
 423                 return;
 424         }
 425         tevent_req_set_callback(subreq, ads_dns_query_srv_done, req);
 426 }
 427
 428 static void ads_dns_query_srv_done(struct tevent_req *subreq)
 429 {
 430         struct tevent_req *req = tevent_req_callback_data(
 431                 subreq, struct tevent_req);
 432         struct ads_dns_query_srv_state *state = tevent_req_data(
 433                 req, struct ads_dns_query_srv_state);
 434         NTSTATUS status;
 435
 436         status = ads_dns_lookup_srv_recv(
 437                 subreq, state, &state->srvs, &state->num_srvs);
 438         if (tevent_req_nterror(req, status)) {
 439                 return;
 440         }
 441
 442         if ((state->num_srvs == 0) || (state->async_dns_timeout == 0)) {
 443                 tevent_req_done(req);
 444                 return;
 445         }
 446
 447         subreq = dns_rr_srv_fill_send(
 448                 state,
 449                 state->ev,
 450                 state->srvs,
 451                 state->num_srvs,
 452                 state->async_dns_timeout);
 453         if (tevent_req_nomem(subreq, req)) {
 454                 return;
 455         }
 456         tevent_req_set_callback(subreq, ads_dns_query_srv_filled, req);
 457 }
 458
 459 static void ads_dns_query_srv_filled(struct tevent_req *subreq)
 460 {
 461         NTSTATUS status = dns_rr_srv_fill_recv(subreq);
 462         return tevent_req_simple_finish_ntstatus(subreq, status);
 463 }
 464
 465 NTSTATUS ads_dns_query_srv_recv(
 466         struct tevent_req *req,
 467         TALLOC_CTX *mem_ctx,
 468         struct dns_rr_srv **srvs,
 469         size_t *num_srvs)
 470 {
 471         struct ads_dns_query_srv_state *state = tevent_req_data(
 472                 req, struct ads_dns_query_srv_state);
 473         NTSTATUS status;
 474
 475         if (tevent_req_is_nterror(req, &status)) {
 476                 tevent_req_received(req);
 477                 return status;
 478         }
 479         if (srvs != NULL) {
 480                 *srvs = talloc_move(mem_ctx, &state->srvs);
 481         }
 482         if (num_srvs != NULL) {
 483                 *num_srvs = state->num_srvs;
 484         }
 485         tevent_req_received(req);
 486         return NT_STATUS_OK;
 487 }
 488
 489 NTSTATUS ads_dns_query_srv(
 490         TALLOC_CTX *mem_ctx,
 491         uint32_t async_dns_timeout,
 492         const char *sitename,
 493         const char *query,
 494         struct dns_rr_srv **srvs,
 495         size_t *num_srvs)
 496 {
 497         TALLOC_CTX *frame = talloc_stackframe();
 498         struct tevent_context *ev = NULL;
 499         struct tevent_req *req = NULL;
 500         NTSTATUS status = NT_STATUS_NO_MEMORY;
 501
 502         ev = samba_tevent_context_init(frame);
 503         if (ev == NULL) {
 504                 goto fail;
 505         }
 506         req = ads_dns_query_srv_send(
 507                 frame, ev, async_dns_timeout, sitename, query);
 508         if (req == NULL) {
 509                 goto fail;
 510         }
 511         if (!tevent_req_poll_ntstatus(req, ev, &status)) {
 512                 goto fail;
 513         }
 514         status = ads_dns_query_srv_recv(req, mem_ctx, srvs, num_srvs);
 515 fail:
 516         TALLOC_FREE(frame);
 517         return status;
 518 }
 519
 520 char *ads_dns_query_string_dcs(TALLOC_CTX *mem_ctx, const char *realm)
 521 {
 522         char *ret = talloc_asprintf(mem_ctx, "_ldap._tcp.dc._msdcs.%s", realm);
 523         return ret;
 524 }
 525
 526 char *ads_dns_query_string_gcs(TALLOC_CTX *mem_ctx, const char *realm)
 527 {
 528         char *ret = talloc_asprintf(mem_ctx, "_ldap._tcp.gc._msdcs.%s", realm);
 529         return ret;
 530 }
 531
 532 char *ads_dns_query_string_kdcs(TALLOC_CTX *mem_ctx, const char *realm)
 533 {
 534         char *ret = talloc_asprintf(
 535                 mem_ctx, "_kerberos._tcp.dc._msdcs.%s", realm);
 536         return ret;
 537 }
 538
 539 char *ads_dns_query_string_pdc(TALLOC_CTX *mem_ctx, const char *realm)
 540 {
 541         char *ret = talloc_asprintf(
 542                 mem_ctx, "_ldap._tcp.pdc._msdcs.%s", realm);
 543         return ret;
 544 }
 545
 546 char *ads_dns_query_string_dcs_guid(
 547         TALLOC_CTX *mem_ctx,
 548         const struct GUID *domain_guid,
 549         const char *realm)
 550 {
 551         struct GUID_txt_buf buf;
 552         char *ret = NULL;
 553
 554         talloc_asprintf(
 555                 mem_ctx,
 556                 "_ldap._tcp.%s.domains._msdcs.%s",
 557                 GUID_buf_string(domain_guid, &buf),
 558                 realm);
 559         return ret;
 560 }